Question

1. what is the formula for potassium sulfate?
2. what is the formula for copper (ii) nitrate?
3. for the compound ni(oh)₂, what is the percent composition for each element?
4. what is the formula for the compound ammonium sulfate?
5. if you have 35 grams of fe(oh)₃, how many molecules do you have?
6. if you have 0.25 moles of na₂s, how many grams and molecules do you have?

16.

Explanation:

10.

Step1: Identify ions

Potassium ion is $K^+$ and sulfate ion is $SO_{4}^{2-}$.

Step2: Balance charges

To balance charges, we need 2 potassium ions for 1 sulfate ion.
$K_2SO_4$

Step1: Identify ions

Copper (II) ion is $Cu^{2 +}$ and nitrate ion is $NO_{3}^{-}$.

Step2: Balance charges

We need 2 nitrate ions for 1 copper (II) ion.
$Cu(NO_3)_2$

Step1: Calculate molar mass of $Ni(OH)_2$

Molar mass of $Ni$: $58.69\ g/mol$, $O$: $16.00\ g/mol$, $H$: $1.01\ g/mol$. Molar mass of $Ni(OH)_2=58.69+(2\times(16.00 + 1.01))= 92.71\ g/mol$.

Step2: Calculate percent composition of $Ni$

$\text{Percent of }Ni=\frac{58.69}{92.71}\times100\%\approx63.31\%$

Step3: Calculate percent composition of $O$

Mass of $O$ in $Ni(OH)_2$ is $2\times16.00 = 32.00\ g/mol$. $\text{Percent of }O=\frac{32.00}{92.71}\times100\%\approx34.52\%$

Step4: Calculate percent composition of $H$

Mass of $H$ in $Ni(OH)_2$ is $2\times1.01 = 2.02\ g/mol$. $\text{Percent of }H=\frac{2.02}{92.71}\times100\%\approx2.18\%$

Answer:

$K_2SO_4$

11.